Flexible displays and miniature cameras made possible by thinnest lens

By Jack Loughran

Published Friday, March 11, 2016

An ultra-thin lens that is just nine atomic layers thick, or one two-thousandth the thickness of a human hair, could be used to create flexible computer displays and miniature cameras.

The 6.3 nanometre lens is significantly daintier than previous ultra-thin flat lenses which were made from comparatively chubby 50-nanometre thick gold nano-bar arrays, known as a metamaterial.

It is made from a compound called molybdenum disulphide which is in a class of materials known as chalcogenide glasses, which have flexible electronic characteristics that have made them popular for components used in high-end devices.

The lens, which was worked on by a team from the Australian National University, was created by peeling off a larger piece of molybdenum disulphide with sticky tape.

They then created a 10-micrometre-radius lens, using a focused ion beam to shave off the layers atom by atom, until they had the dome shape of the lens.

The team discovered that single layers of molybdenum disulphide, 0.7nm thick, had remarkable optical properties, appearing to a light beam to be 50 times thicker, at 38nm. This property, known as optical path length, determines the phase of the light and governs interference and diffraction of light as it propagates.

A simulation showed that light bounced back and forth many times inside the high-refractive-index crystal layers before passing through.

The high refractive index means the material is perfectly suited to camera lenses while its flexibility could allow for the construction of bendable displays.

"Molybdenum disulphide is an amazing crystal," said lead researcher Dr Yuerui Lu.

"It survives at high temperatures, is a lubricant, a good semiconductor and can emit photons too.

"The capability of manipulating the flow of light in atomic scale opens an exciting avenue towards unprecedented miniaturisation of optical components and the integration of advanced optical functionalities."